feat(export-invoice-fees): Export invoice fees to CSV (#2268)

## Roadmap Task

👉
https://getlago.canny.io/feature-requests/p/ability-to-export-data-from-the-user-interface

## Context

In order to effortlessly download export of invoice fees by
non-technical users, it is required to add a new CSV exporter and extend
the export resource service and mailer.

## Description

This change adds a new CSV exporter for invoice fees;

also extends the `ExportResourcesService` to handle unknown resource
types and invoice_fees.

and improve the mailer and its specs to support different kind of
exported resources like invoice_fees.

app/mailers/data_export_mailer.rb

@@ -3,6 +3,7 @@
 class DataExportMailer < ApplicationMailer
   def completed
     @data_export = params[:data_export]
+    @resource_type = @data_export.resource_type.humanize.downcase
     user = @data_export.user
 
     return if @data_export.file.blank?
@@ -15,7 +16,7 @@ def completed
         from: ENV['LAGO_FROM_EMAIL'],
         subject: I18n.t(
           'email.data_export.completed.subject',
-          resource_type: @data_export.resource_type
+          resource_type: @resource_type
         )
       )
     end

app/services/data_exports/csv/invoice_fees.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require 'csv'
+require 'forwardable'
+
+module DataExports
+  module Csv
+    class InvoiceFees < Invoices
+      extend Forwardable
+
+      def call
+        ::CSV.generate(headers: true) do |csv|
+          csv << headers
+
+          query.invoices.find_each do |invoice|
+            serialized_invoice = serializer_klass
+              .new(invoice, includes: %i[fees subscriptions])
+              .serialize
+
+            subscriptions = serialized_invoice[:subscriptions].index_by do |sub|
+              sub[:lago_id]
+            end
+
+            serialized_invoice[:fees].each do |serialized_fee|
+              subscription_id = serialized_fee[:lago_subscription_id]
+              serialized_subscription = subscriptions[subscription_id]
+
+              csv << [
+                serialized_invoice[:lago_id],
+                serialized_invoice[:number],
+                serialized_invoice[:issuing_date],
+                serialized_fee[:lago_id],
+                serialized_fee[:item][:type],
+                serialized_fee[:item][:code],
+                serialized_fee[:item][:name],
+                serialized_fee[:item][:invoice_display_name],
+                serialized_fee[:item][:filter_invoice_display_name],
+                serialized_fee[:item][:grouped_by],
+                serialized_subscription&.dig(:external_id),
+                serialized_subscription&.dig(:plan_code),
+                serialized_fee[:from_date],
+                serialized_fee[:to_date],
+                serialized_fee[:total_amount_cents],
+                serialized_fee[:total_amount_currency],
+                serialized_fee[:units],
+                serialized_fee[:precise_unit_amount],
+                serialized_fee[:taxes_amount_cents]
+              ]
+            end
+          end
+        end
+      end
+
+      private
+
+      def headers
+        %w[
+          invoice_lago_id
+          invoice_number
+          invoice_issuing_date
+          fee_lago_id
+          fee_item_type
+          fee_item_code
+          fee_item_name
+          fee_item_invoice_display_name
+          fee_item_filter_invoice_display_name
+          fee_item_grouped_by
+          subscription_external_id
+          subscription_plan_code
+          fee_from_date
+          fee_to_date
+          fee_total_amount_cents
+          fee_amount_currency
+          fee_units
+          fee_precise_unit_amount
+          fee_taxes_amount_cents
+        ]
+      end
+    end
+  end
+end

app/services/data_exports/export_resources_service.rb

@@ -5,6 +5,8 @@ class ExportResourcesService < BaseService
     EXPIRED_FAILURE_MESSAGE = 'Data Export already expired'
     PROCESSED_FAILURE_MESSAGE = 'Data Export already processed'
 
+    ResourceTypeNotSupportedError = Class.new(StandardError)
+
     def initialize(data_export:)
       @data_export = data_export
 
@@ -42,6 +44,11 @@ def call
     def file_data
       case data_export.resource_type
       when "invoices" then Csv::Invoices.call(data_export:)
+      when "invoice_fees" then Csv::InvoiceFees.call(data_export:)
+      else
+        raise ResourceTypeNotSupportedError.new(
+          "'#{data_export.resource_type}' resource not supported"
+        )
       end
     end
 

app/views/data_export_mailer/completed.slim

@@ -20,7 +20,7 @@ div style='margin-bottom: 32px;width: 80px;height: 24px;'
 div style='margin-bottom: 24px;font-style: normal;font-weight: 400;font-size: 16px;line-height: 24px;color: #19212E;'
   = I18n.t('email.data_export.completed.greetings')
 div style='margin-bottom: 32px;font-style: normal;font-weight: 400;font-size: 16px;line-height: 24px;color: #19212E;'
-  = I18n.t('email.data_export.completed.intro')
+  = I18n.t('email.data_export.completed.intro', resource_type: @resource_type)
 table style='margin-bottom: 32px' width="100%" cellspacing="0" cellpadding="0"
   tr
     td

config/locales/en/email.yml

@@ -16,7 +16,7 @@ en:
       completed:
         fallback_text: If the link has expired, please generate a new one from your Dashboard.
         greetings: Hello
-        intro: Your invoices export is ready! You can download it using the link below, which will be available for 7 days.
+        intro: Your %{resource_type} export is ready! You can download it using the link below, which will be available for 7 days.
         lago_team: The Lago Team
         main_cta_label: Download export
         subject: Your Lago %{resource_type} export in ready!

spec/mailers/data_export_mailer_spec.rb

@@ -9,9 +9,27 @@
 
   describe '#completed' do
     let(:mailer) { data_export_mailer.with(data_export:).completed }
+    let(:file_url) { "https://api.lago.dev/rails/active_storage/blobs/redirect/eyJf" }
+
+    before do
+      allow(data_export).to receive(:file_url).and_return(file_url)
+    end
 
     specify do
       expect(mailer.to).to eq([data_export.user.email])
+      expect(mailer.subject).to eq("Your Lago invoices export in ready!")
+      expect(mailer.body.encoded).to match("Your invoices export is ready!")
+      expect(mailer.body.encoded).to match("will be available for 7 days")
+      expect(mailer.body.encoded).to match(data_export.file_url)
+    end
+
+    context "when the resource type is invoice_fees" do
+      let(:data_export) { create(:data_export, :completed, resource_type: 'invoice_fees') }
+
+      specify do
+        expect(mailer.subject).to eq("Your Lago invoice fees export in ready!")
+        expect(mailer.body.encoded).to match("Your invoice fees export is ready!")
+      end
     end
 
     context 'when data export is expired' do